Prime numbers of the form 4^k +- 3.

Terms

a(0) =7a(1) =13a(2) =19a(3) =61a(4) =67a(5) =1021a(6) =4093a(7) =4099a(8) =16381a(9) =65539a(10) =262147a(11) =1048573a(12) =4194301a(13) =16777213a(14) =268435459a(15) =1073741827